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By Root 302 0

worked in humans, enrolling 30,769 children in Tbilisi. Once a week, about half the children swallowed a pill that contained phages against Shigella. The other half of the children got a pill made of sugar. To minimize environmental influences as much as possible, the Eliava scientists gave the phage pills only to children who lived on one side of each street, and the sugar pills to the children who lived on the other side. The scientists followed the children for 109 days. Among the children who took the sugar pill, 6.7 out of every 1,000 got dysentery. Among the children who took the phage pill, that figure dropped to 1.8 per 1,000. In other words, taking phages caused a 3.8-fold decrease in a child’s chance of getting sick.

Few people outside of Georgia heard about these striking results, thanks to the secrecy of the Soviet government. Only after the Soviet Union fell in 1989 did news start to trickle out. The reports have inspired a small but dedicated group of Western scientists to investigate phage therapy and to challenge the long-entrenched reluctance in the West to use them.

These phage champions argue that we should not be worried about using live viruses as medical treatments. After all, phages swarm inside many of the foods we eat, such as yogurt, pickles, and salami. Our bodies are packed with phages too, which is not surprising when you consider that we each carry about a hundred trillion bacteria—all promising hosts for various species of phages. Every day, those phages kill vast numbers of bacteria inside our bodies without ever harming our health.

Another concern that’s been raised about phages is that their attack is too narrowly focused. Each species of phage can only attack one species of bacteria, while one antibiotic can kill off many different species at once. But it’s clear now that phage therapy can treat a wide range of infections. Doctors just have to combine many phage species into a single cocktail. Scientists at the Eliava Institute have developed a dressing for wounds that is impregnated with half a dozen different phages, capable of killing the six most common kinds of bacteria that infect skin wounds.

Skeptics have also argued that even if scientists could design an effective phage therapy, evolution would soon render it useless. In the 1940s, the microbiologists Salvador Luria and Max Delbruck observed phage resistance evolving before their own eyes. When they laced a dish of E. coli with phages, most of the bacteria died, but a few clung to existence and then later multiplied into new colonies. Further research revealed that those survivors had acquired mutations that allowed them to resist the phages. The resistant bacteria then passed on their mutated genes to their descendants. Critics have argued that phage therapy would also foster the evolution of phage-resistant bacteria, allowing infections to rebound.

The advocates for phage therapy respond by pointing out that phages can evolve, too. As they replicate, they sometimes pick up mutations, and some of those mutations can give them new avenues for infecting resistant bacteria. Scientists can even help phages improve their attacks. They can search through collections of thousands of different phages to find the best weapon for any particular infection, for example. They can even tinker with phage DNA to create phages that can kill in new ways.

In 2008, James Collins, a biologist at Boston University, and Tim Lu of MIT published details of the first phage engineered to kill. Their new phage is especially effective because it’s tailored to attack the rubbery sheets that bacteria embed themselves in, known as biofilms. Biofilm can foil antibiotics and phages alike, because they can’t penetrate the tough goo and reach the bacteria inside. Collins and Lu searched through the scientific literature for a gene that might make phages better able to destroy biofilms. Bacteria themselves carry enzymes that they use to loosen up biofilms when it’s time for them to break free and float away to colonize new habitats. So Collins